<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<p id="tel_demo_text">我在聚焦输入框时消失</p>
<label for="tel_input">电话号码</label>
<input type="text" id="tel_input">
<p id="tel_warn_text" style="display: none">我在聚焦输入框时出现</p>
<script src="script.js"></script>
</body>
</html>